Hotspots of acceleration and demographic processes behind decline of North American birds

François Leroy , Marta A. Jarzyna, Petr Keil

Human activities might have accelerated declines of population abundances, but this acceleration remains underexplored. Using the North American Breeding Bird Survey, we analyze abundance changes, acceleration, and demographic processes of recruitment and loss across 234 bird species from 1987 to 2021. We show a continent-wide decline of bird abundance, with hotspots of acceleration in the Mid-Atlantic, Midwest, and California, matching patterns of agricultural activities. In California and the Midwest, increasing loss rates drive acceleration, while in the Mid-Atlantic, declining recruitment is the main process behind the acceleration. Notably, 67% of increasing species and 95% of increasing families show declining recruitment rates, underscoring the need for conservation policies that enhance recruitment, not just prevent loss, even for seemingly thriving species.